1. Field of the Invention
The present invention relates to a wire bonding apparatus and, more particularly, to target path generating means for generating a target path indicating a motion process of an XY stage and a capillary.
2. Description of Related Art
FIG. 1 is a block diagram of a conventional wire bonding apparatus. In FIG. 1, an XY stage 102 is driven in an X-axis direction horizontally and in a Y-axis direction horizontally by an XY drive motor 101 to move a capillary 104 in the X-axis direction horizontally and in the Y-axis direction horizontally. The capillary 104 is driven in a Z-axis direction vertically by a Z-axis drive motor 103. Also, sensors, not shown, are disposed on the X-, Y-, and Z-axes so that the positions of the XY stage 102 on the X- and Y-axes and the position of the capillary 104 on the Z-axis can be detected. A servo computation section 105 is provided, which reads position signals X, Y and Z obtained by the sensors, and computes and outputs proper driving force signals 106a, 106b and 106c to follow a target path 109. The target path 109 is generated and outputted by a target path generating section 108, described later, to indicate each motion process of the XY stage 102 and the capillary 104. Amplifiers 107a, 107b and 107c are provided for amplifying the driving force signals 106a, 106b and 106c, respectively, and for supplying the amplified signals to the XY drive motor 101 and the Z-axis drive motor 103. By the output signals sent from the amplifiers 107a, 107b and 107c, the XY stage 102 and the capillary 104 are driven according to the target path 109, by which wire bonding is performed between an electrode on a semiconductor chip and a package lead.
The target path 109 for the XY stage 102 and the capillary 104 can be generated by various methods. Theoretically, the path for driving at the highest speed is a rectangular path by the input of the fastest acceleration. In the case where a fixed driving force is supplied, however, since the driving force signals 106a, 106b and 106c contain high-frequency components in large amounts, a vibration mode existing in the XY stage 102 and the capillary 104 is excited, which causes a problem in that much time is taken until vibrations cease. Also, there arises a problem in that the vibrations cause poor bonding.
To cope with such problems, the art described in Japanese Laid Open Patent Publication No. 6-310556 uses a cycloid path (sinusoidal path) to generate the target path 109. When such a path is used, the driving force signals 106a, 106b and 106c are composed of a single frequency component only, so that there is less possibility of exciting the vibration mode existing in the XY stage 102 and the capillary 104. Therefore, the target path 109 can be followed steadily. With this method, however, when the drive speed of the bonding apparatus is increased, the period of a sinusoidal wave used for the path is shortened, so that the vibration mode of the XY stage 102 and the capillary 104 is excited. Therefore, there is a possibility of causing the same problems as described above.
Also, for the wire bonding apparatus, the XY stage 102 and the capillary 104 are mainly subjected to reciprocating motion because of their characteristics. Conventionally, however, the target path has been prepared individually for each motion. Therefore, if the period of a sinusoidal wave used for an acceleration path is short, there is a possibility of exciting the vibration mode of the XY stage 102 and the capillary 104.
As described above, the conventional wire bonding apparatus has a problem in that when an increased speed of the apparatus is attained, the vibration mode of the XY stage and capillary is excited, so that the stability is impaired.
Therefore, an object of the present invention is to provide a wire bonding apparatus operated steadily at a high speed without excitation of vibrations of an XY stage and a capillary, which are movable parts.
To achieve the above object, the invention of a first mode is characterized in that in a wire bonding apparatus which has an XY axis driving mechanism and a Z axis driving mechanism for driving an XY stage and a capillary, respectively, and connects a wire between an electrode on a semiconductor chip and a wiring layer or a lead of a package by controlling the XY stage and capillary so that they go along a target path specified in advance. The apparatus comprises composite target path generating means for generating the target path, in which the deceleration part of a go path and the acceleration part of a return path are one continuous path, for a path part of reciprocating movement of the target path indicating a motion process of either one or both of the XY stage and capillary.
The invention of a second mode is characterized in that in the wire bonding apparatus of the first mode, the composite target path generating means generates the target path, in which the deceleration part of the go path and the acceleration part of the return path for the path part of the reciprocating movement is one continuous path so that the fastest acceleration is within the fastest acceleration that can be produced by the XY axis driving mechanism and Z axis driving mechanism.
The invention of a third mode is characterized in that in the wire bonding apparatus of the first mode, the composite target path generating means generates the target path, in which the deceleration part of the go path and the acceleration part of the return path are one continuous path for the path part of the reciprocating movement so that the fastest acceleration does not exceed the fastest acceleration that can be produced by the XY axis driving mechanism and Z axis driving mechanism, and that the acceleration period of the target path is within the time specified in advance.
The invention of a fourth mode is characterized in that in the wire bonding apparatus of the first, second, or third mode, the target path is a target acceleration path, target velocity path, and target position path.
The invention of a fifth mode is characterized in that in the wire bonding apparatus of the fourth mode, the target acceleration path is a cycloid path of a sinusoidal wave.
The invention of a sixth mode is characterized in that in the wire bonding apparatus of the fourth mode, the target acceleration path is a rectangular wave path.
The invention of a seventh mode is characterized in that in the wire bonding apparatus of the fourth mode, the target acceleration path is a triangular wave path.
The invention of a eighth mode is characterized in that in the wire bonding apparatus of the fourth mode, the target acceleration path is a continuous path formed by a combination of two or more paths of the cycloid path, rectangular wave path, and triangular wave path.